Một điều cần tìm trong một ổ đĩa cứng là bộ nhớ cache. Cache là nơi lưu trữ bổ sung trên ổ đĩa, bao gồm một số lượng bộ nhớ (bộ nhớ đặc biệt, không thường xuyên máy tính RAM). Bộ nhớ được | Chapter 7 Disks of Every Type Permanent Storage 69 CD-R drives have two X numbers such as 8 12. The lower number is the speed at which the drive can write information. The higher number is the speed at which data can be read. To put this concept in practical terms to record an hour s worth of music on CD-R that can write at 12X takes you only 5 minutes. That s 12 times faster than 1X which takes one hour to write one hour s worth of music. CD-R RW drives have a third X number which is the speed at which the RW drives are written to. This number is different from the CD-R value because CD-RW disks are written to in a different manner from CD-R discs. DVDs DVD-Rs They don t have X values listed. Supposedly they re all just fast. Cache or buffer memory Another thing to look for in a hard drive is the cache memory. The cache is a supplemental storage place on the drive composed of a given amount of memory special memory not regular com- puter RAM . That memory is used to speed up the drive by storing ---- often-read information in the cache memory. Reading the information from cache memory rather than from the disk itself can markedly increase the hard drive s performance. The larger the cache memory on a disk drive the better. A minimum a hard drive should have a 2MB cache. Top-of-the-line models may have as much as 8MB of cache memory. That s good. Cache is pronounced cash. A hard drive cache may also be called buffer memory. Other disk drives may also use cache memory. Again More is better. Bottom line The higher the value for cache memory the better. Fixed or removable Is your hard drive fixed Probably. Betcha didn t even know it was broken Ha-ha. Oh my sides. 70 Part II Hardware and Software Overview Three more confusing disk drive terms Computer jargon is endless. There s no need ever for you to memorize any computer term as long as you have a computer dictionary handy like the Illustrated Computer Dictionary For Dummies which I wrote from Wiley Publishing Inc. .